Method of heating, hardening, and tempering of hollow steel propeller blades



Aug. 1, 1933. J. H. Mmes` METHOD OF HEATING',l HARDENING', AND TEMPERINGOF HOLLOW STEEL=PROPELLER BLADES Filed April `5. 1932 aux L L L' wwzamj'@Anoxym ,Y

Patented Aug. 1, 1933 I I1,920,652.` 'METHOD or HEATING, HARDEN'ING,

Ann

"TEMPERING A 0F -HoLLow STEEL" Pno- PELLER BLADES .Y

f James H. McKee, Pittsburgh, Pa-assignor to Pittsburgh Screw and BoltCorporation, a Cor f y A A,porationfof Pennsylvania y l ApplicationApril 5,1932.y Serial 1710.116032 59' v n *4 enum.;l (ci. lss-zn IThisinvention relates to aeronautical pro-v pellers, and moreparticularly-to improvements;Y in the' method of hardening l andtempering de. V

' jig 14,may be of any lsuitable construction I pretachable hollow steelpropeller blades.r

`One f object of this invention ris to provide a method for producingstraight propeller blades Vhaving the desired hardness and temper.

Another Aobject of this invention is'to provide. a`

novel method for' tempering and hardening hol- 0 low steel propellerblades whereby practical y straight blades can be produced.v 'v I amethdfor hardening and tempering propeller blades in which the bladesare so held during the quenching and coolingl operations thatwarping`thereof is prevented.

These and other objects which Will'be made ap parent to those skilled inthis particular-art are accomplished by means off" this invention, thesteps of vwhichy are described i'ntheffollowing specification andillustratedin theaccompanying drawing, wherein:

Figure 1 is-a view. in vertical section of a heat-l ing furnaceillustrating therst step in myl pIOCeSS;

Fig. 2 is a view in end elevation` illustrating thelheld. duringapparatus in which, the blade is quenching and air cooling;` Y. 1

rig. a is a view msildeleievaun or nie made holding apparatus; f f i. I

Fig. 4 is avviewin vertical, sectionfof adraw' heating furnace; 'f

Fig. 5 is an enlarged partial view section .of

the'blade holding apparatus;

elevation of the Fig.A 6 is -an enlarged view in side base of the bladeholding apparatus;V

Fig. '7 is a sectional view taken on llneVIlI-VII of Fig. 6;

Fig. 8 is a sectional view talreiizon line VIIIofFlg.6; y Fig. 9 is asectional view on' linek of Fig. d; and l y Fig. 10 is a sectional viewtake'lron'line 1p1-,X

ofFig.6.

In carrying out my porting the blades during these operations. After thering 1l has been secured tothe blade. 10, ltjis suspended from a spider12 and lowered into a vertical heating furnace 13 of any suitable type 5such as an electric furnace, where it is heated or raised to atemperature or about 1650 to 17oo F.

temperature it is removedfiom thefurnace 13 and placed ina-straightening jig 14. vWhile the l15er `to use a Jig such asisdescribed in my co- -pending application Serial No. v603,258, filed'April 5, 1932, which comprises a base member 14a lhaving a perforatedportionvshaped to conform ln contour to one face of a propeller bladeand j onwhich the heated blade is placed. The blade J .is held on themember 14a `by a series of yokes A further object of `this invention isto provide 14b extending transversely of the plate 14a and which areadapted to be moved into engagement with the edges of theblade tosecurely clamp it against Vthe member14a. The `yokes 14h are movedintoand out of engagement with .the edges ofthe blade-by air `motors 14cmounted on a frame 14d supporting the;base member 14a. The air motorsare connected to the yokes 14bby pis- 'ton rods 14e. The.- air motorsare supplied with air from a suitable sourcevof supply through -pipes14f. After'the bladehas-been heated it is -in .the air jig 141it ishardened` by submerging in a vtank 15 containing oil or other suitablequenchingliquid.v r f In order that the air jig A.14 may be readilylowered into the tank 15,1when the blade has been *clamped thereinytheJig-14 is'supported on a bar 16 whichis joumaled in trunnions 17slidably l mounted on uprights 18A `which extend down- `wardlyintotheuid inthe tank 15. As shown in Figure 3, the-air :jig .14,is so mountedon the vbar 1,6v that lthe portion thereof adapted to receive the shankof the bladeis over the tank 15and the center of mass of the jig issubstantially over thebarl. 'l I' p In order to prevent thevweightof theJig 14 from moving thebar downwardly on the uprights 18, the b ar16`ls'also lpl'voted in the endsof strap members 19 depending from acounterbalanced Acrossbar'ZO; The cross bar 201s slidablymounted'ontheuprights18 and has cables. 21 attached thereto which passover pulleysj22 `and 23 and are fastened to counterweights 24'.The*d ofthe yair-clamping jig l14, when'infblade receiving posi'- tion, issupported on af'suitable standard 25.

When the blade has been clamped ln the airclamping device 14 and itisdesired tolower the blade andjig into the oil or quenching liquid inthe tank l5, the tip receiving end of the air jig is pushed upwardlybythe operator so that the bar -After the blade; lo hasbeen raised tohardening 33 where it is'heated blades without departing Asince theyokes of' .tain changes may 16 is turned in its trunnions 17. As the tipend of the air-jig is raised the center of mass of the jig shifts towardthe uprights 18, overcomes the counterbalance weights 24 and the bar 16carry-I ing the jig slides downwardly on the uprights 18 into the tank15 until it comes to rest on a spring bumper 26 disposed in the bottomof the tank between the uprights 18.

Since the hollow blade is submerged in the tank with the shank end down,it is apparent that the oil or quenching liquid in the tank passes intothe interior of the blade as Well as around the outer surface thereofand as a result all parts of the .blade are given substantially the samedegree o! hardness.

After the blade has been a cable 27 passing around pulleys 28 and 29 andhaving one end thereof attached to a suitable winch (not shown) and theother end to the cross-head 20 -isv wound von the winchand pulls theair-jig -14 out of the tank 15. As the airclamping device-moves upwardlybetween the upe rights 1S, the end of the jig 14 engages curved slides30 mounted adjacent to the uprights 18 and the tip end of theair-clamping device is forced away from the uprights which shifts thecenter of mass and causes the jig to fall on the support 25. Y

The blade 10 is jig 14 and is suspended a suitable spider 32 in thenremoved from the airthrough the ring 11 from a vertical draw furnace toa temperature of b etween 900 and 1200 .for approximately 3 to 4 hours.After the blade has beenthoroughly soaked in the -draw furnace 33 it isremoved therefrom and placed in another clamping jig similar in allrespects to the one in which it was held during the Vquenching operationwhere it is allowed to cool slowly in the air to give it the propertemper'. u

By holding the blade in such a clamping device during the quenching andair cooling operation, it is readily apparent that I am able to preventthe tip end of the blade from curlling and the body of the blade fromwarping blade by al continuing pressure they follow up the contractionor shrinvage of the blade, and as a result I am .able to producepractically straight hardened* and tempered propeller blades having theproper curvature for any transverse section thereof.

While I have described one embodimentof my invention, it is readilyapparent that cerbe made in the steps of my method for hardening andtempering propeller from the spirit of my thoroughly quenched,

three hours, -and the .jig are held against the invention or the scopeof the appended claims.

-transverse sections of the blade during the yquenching operation,reheating the blade between a temperature of 900 to 1200 F., and thencooling the blade slowly while applying pressure tosucceeding-transverse sections thereof.

' y2. The method of hardening and tempering hollow steel propellerblades, which consists in heating ajblade to a hardening temperature ofat least 1650, dipping said heated blade shank lend first in an oil bathto harden both the inner and outer surfaces thereof, holding the edgesofthe blade under continuous.r pressure during the quench `to preventwarping, soaking the blade for about three hours at a temperature of atleast 900, cooling the reheated blade in air to temper the same, andapplying continuouspressure to the edgesoi.' the blade while it iscooling to follow up contraction and shrink- `age therein and preventwarping of the blade.

heating ,a blade to approximately 1650", dipping said heated blade shankend first in a quenching liquid, applying pressure to the solid edges ofsucceeding transverse sections of the blade while in the quench, raisingthe quenched blade to a temperature between 900 'and 1200, holding theblade at suchv temperature for at least cooling the blade .in air whilesucceeding transverse sections thereof are Vsub-l jected to pressure-toprevent warping of the blade.

4. The method of hardening and tempering :hollow steel propeller bladeswhich consists in heating a blade to approximately 1650, dipping saidheated blade shankA end first in a quenching liquid, applying continuouspressure to the solid edges of succeeding transverse sections of theblade while in the quench, raising the quenched blade to a temperaturebetween 900 and 1200*?, holding the blade-at such temperature for atleast three hours cooling the blade in air, and continuously applyinglpressure to the solid edges of said blade as-it is being cooled tofollow up the shrinkage therein and prevent the blade from warping outof shape.` f

cAMEs H. MCKEE.

